html,
body {
    width: 100%;
    height: 100%;
    font-family: "Helvetica Neue", Helvetica, STHeiTi, sans-serif;
    overflow: hidden;
    background: #fff;
    margin: 0;
    padding: 0;
}
*{
  margin: 0;
  padding: 0;
}
.main {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
}
.main img {
    width: 100%;
    height: 100%;
}
canvas{
    width:100%;
    height:100%;
    position: absolute;
    top:50%;
    left:50%;
    transform: translate(-50%,-50%);
}